Efficient bidirectional energy exchange between an alternating current (AC) grid and a direct current (DC) source has been enabled through advanced power converter topologies. In this study, a single-stage AC-DC dual active bridge (DAB) converter employing phase-shift modulation (PSM) was investigated, with a particular focus on performance within the overmodulation regime. Bidirectional switching modules were implemented on the AC side to facilitate seamless energy transfer. Two conventional modulation strategies—sinusoidal and triangular—and a novel back-calculated modulation method were examined for their performance in both linear and overmodulation operating regions. The proposed back-calculation method incorporates an off-line generated reference current waveform designed to approximate linear control characteristics while substantially minimizing current harmonic distortion under overmodulated conditions. This approach extends the linear relationship between the reference current and power transfer capability beyond the conventional modulation limits, thereby enhancing converter performance in high-demand scenarios. Simulation-based analysis demonstrated that, in the linear region, the proposed method reduced average current total harmonic distortion (THD) by at least 45% when compared to conventional sinusoidal and triangular modulation techniques. Moreover, within the overmodulation regime, the linear correlation between the reference current and power transfer was extended by approximately 16.5%. The current harmonic distortion remained below 5% and 8% at modulation ratios of 108% and 112%, respectively, underscoring the robustness of the proposed strategy. These results suggest that the proposed PSM method is highly effective in achieving improved power exchange with reduced harmonic content in both linear and overmodulated operation, thereby offering a viable solution for high-performance AC-DC power conversion in smart grids and renewable energy systems.